Method and system for setting the hydraulic pressure influencing a grab member

ABSTRACT

The object of the invention is a method and a system for setting the hydraulic pressure influencing a hydraulic grab member by using adjustment members. The setting of the maximum value of the pressure takes place automatically by reading the identifying information on the piece (6) being handled by means of a reading device (1), on the basis of which the control unit (3) linked to the reading device (1) directs the adjustment member (4). When the operator of the system starts raising the hydraulic pressure from the hydraulic tank (13) by means of the operating valve (9) of the grab member (5), the adjustment member (4) limits the hydraulic pressure going to the compression cylinder (8) of the grab member (5) and thus a compressive force of the correct magnitude is directed onto the piece (6) being handled.

The object of this invention is a method and system for setting thehydraulic pressure influencing a hydraulic grab member, in particularroll jaws, by using control members.

In various kinds of equipment handling single pieces, such as also inmore extensive systems handling pieces, various kinds of operations arecarried out, in which the force acting as a pressure on a piece isadjusted by controlling the hydraulic pressure influencing the hydrauliccylinder of the grab member. One example of equipment handling thesekinds of pieces is a truck equipped with roll jaws or other appropriategrab member used in handling rolls of paper.

In present methods, the hydraulic pressure influencing the grab memberis selected manually. The person driving the device handling the piecemust, on the basis of the information that he has received, select whatis to his mind an appropriate hydraulic pressure, which is directed toinfluence the grab member, and thus also the mechanical compressiveforce directed on the piece corresponding to the hydraulic pressure.

In this kind of system, which is based on manual pressure selection, theproblem is precisely the manual form of operation, when the person isthe factor in the system due to which undesirable results occur. In amanual system, handling mistakes take place, due to indifference andforgetfulness, as a result of which the mechanical compressive forcedirected onto the piece is wrong, often being too great, when the pieceis damaged due to too great pressure.

For example, the trucks in use handling rolls of paper damage them insuch a way that they cannot be used in the printing presses of anewspaper publisher, for even a depression of five millimeters caused byexcessive compression may cause the rejection of the roll.

The intention of this invention is to create a method that avoids theaforementioned defects, and which makes it possible to set the hydraulicpressure influencing the grab member in such a way that such amechanical compressive pressure is directed onto the piece withoutdamaging it.

This intention is achieved by means of the method in accordance with theinvention, of which it is characteristic that in the method identifyinginformation is read by a reading device from an identifier on the piecebeing handled and that a control device setting the hydraulic pressureinfluencing the grab member is controlled by the identifying informationand thus it also sets the compressive force directed onto the piece.

The method in accordance with the invention is based on the idea thatthe correct mechanical compressive force, which is directed onto thepiece being handled is set automatically on the basis of the informationread from the identifier on the piece.

By means of this method the possibility of the human error factor isremoved, as in this method the setting of the maximum value is based onthe information contained in the identifier, and not on a human choice.

It is further also possible to remove the errors in handling caused byhuman forgetfulness. Considerable economic savings can be achievedthrough the reduction of damage to the pieces being handled.

The object of the invention is also a system for setting the hydraulicpressure influencing a hydraulic grab member, which system consists ofan adjustment member. It is characteristic of the system in questionthat a control unit is connected to the adjustment device, the controlunit being connected to a reading device, which reads the identifier onthe piece being handled, which either directly or indirectly states thepressure which may be directed onto the piece by the grab member.Generally the operating device used is a hydraulic cylinder, thegreatest operating pressure of which is controlled according to theidentifier information.

By means of a system of this kind it is possible to implement theconstructions required by the pressure setting method and thus achievethe advantages offered by the method with an appropriately compactconstruction, one significant advantage of the construction being thatfor example when handling rolls of paper, rolls with varying compressionresistant properties can be handled by the same truck in such a way thatthe rolls of paper are not damaged.

The invention is described in greater detail with the aid of thefollowing examples of forms of application with reference to theaccompanying figures.

FIG. 1 shows the method in accordance with the invention and a schematicdiagram for a system in accordance with the method.

FIG. 2 shows an adjustment member consisting of a four-placepressure-selection valve.

FIG. 3 shows a re-connectable, steplessly adjustable adjustment member.

The method in accordance with the invention and a system forimplementing the method can be used with various kinds of devices forhandling different pieces, of which one that is shown is a truck usedfor handling papers rolls, without, however, limiting the invention tothis purpose.

Here the system implementing the method is located in a conventionalhydraulic system using roll jaws 5', which here is shown considerablysimplified. The figure does not show among other things the conventionalprotection devices for the pump, which have no significance from thepoint of view of the invention.

Paper rolls are handled by means of a truck using the aforementionedroll jaws 5'. In FIG. 1 the grab member is marked by the referencenumber 5 in general, and here roll jaws in particular by the referencenumber 5'. The roll jaws 5' consist of a moving jaw 5a operated by apiston rod 5b and a fixed jaw 5c to which the frame section 5a of thecylinder 8 is also attached. By feeding oil to the connection on thepiston rod 5b side, i.e. to the hydraulic line 15, the jaws 5a and 5b ofcylinder 8 begin to approach one another and press the roll 6 betweenthem.

As in a conventional system, pressurized oil produced by a hydraulicpump 7 is led through a three-way operating valve to one or other of theconnections, i.e. hydraulic lines 15 or 16, or to the return line 14.Here the hydraulic pump 7 draws the oil through hydraulic line 12 directfrom the hydraulic tank 13, without a separate feed pump.

The system in accordance with the invention is constructed between thecompression side hydraulic line 15 and the return line 14 of thecompression cylinder 8. In place of the return line it is possible toalso use the hydraulic line leading directly to the tank, or generallyany low-pressure return side line at all.

In the system implementing the method in accordance with the inventionshown in the figures the reading device 1 reads the informationcontained in the identifier 2 in the piece 6 being handled, in this casea roll of paper. The identifier 2 may be attached or marked also on theprotective wrapping of the piece 6 being handled, the transport base, orsome other place, from which the identifier 2 can be easily read whenthe piece 6 is being handled. The identifier 2 either directly orindirectly expresses the maximum value of the compressive pressure thatcan be directed onto piece 6, without it being in danger of beingdamaged. In this connection the term `indirect expression` means thatthe identifier contains information for example of the type of the piece6 being handled or of some other factor, on the basis of which the piece6 being handled and thus also of the compression-resistance propertiesof the piece 6 being handled can be recognized.

The identifier 2 to be read by the reading device 1 can be realized forexample by a bar code, an infra-red identifier, accompanying memory orother identifier suitable for the purpose. The reading device 1 thuscorresponds to the type of the identifier 2 and is for example a barcode reading device, an infra-red identifier reading device, anaccompanying memory reading device, or other reading device suitable forthis purpose.

The reading device 1 and the control unit 3 can be realized using barcode readers manufactured by SAAB AUTOMATION AB, e.g. the CCD cameramodel PANT-120. The truck terminal 9450 manufactured by the INTERMEKCorp. can also be used here.

The identifier 2 is advantageously attached to the piece 6 to be handledin such a way that when handling the piece 6 with the roll jaws 5' theidentifier 2 is not covered by the roll jaws 5'. The identifier 2 issufficiently large in size so that the identifier 2 can be easily readby the reading device 1, without special movements being required to bemade to the piece 6 to be handled.

The reading device 1 is attached to the truck, advantageously to theroll jaws of the truck, in such a way that before gripping the paperroll, or at the initial stage of gripping it, the identifier 2 attachedto the paper roll can be easily read by the reading device 1.

The connection 10 between the reading device 1 and the control unit 3 isadvantageously implemented by a wireless form of communication, forexample by an optic or radio frequency transmitter--receivercombination.

In the second advantageous form of application the connection betweenthe reading device 1 and the control unit 3 is formed by a simple cable.

The control unit 3 is realized by, for example, a programmablemicro-circuit, which is programmed in such a way that, on the basis ofthe information read from the identifier 2, the control unit 3 directsthe adjustment device 4 so that the adjustment device 4 sets the maximumpressure to correspond to the identifier information and further to thecompression-resistance properties of the paper roll. The adjustmentmember 4 consists of two parts--an electrically controlled shut-offvalve 17 and a safety valve 18.

In one advantageous form of application in accordance with the inventionthe control unit 3 is connected to an adjustment device 4, which isformed of two or more, advantageously of four, electrical pressurevalves 4a-4d, adjusted in steps in relation to one another, each ofwhich is connected to hydraulic lines 14 and 15. The stepped settingsare based on the known various compression-resistance properties of thedifferent kinds of pieces to be handled.

The control unit 3 selects through the connection 11 one of theelectrically controlled pressure valves 4a-4d of the adjustment device4, which are adjusted to different opening pressures and in which casethe pressure value of the pressure valve corresponds to the identifierinformation. The other valves remain closed at the same time as theselected pressure valve begins to control the pressure of the hydraulicline 15. Each pressure valve 4a-4d here too consists of two parts--anelectrically operated shut-off valve 17a-17d and a safety valve 18a-18d.

The pressure valves 4a-4d are most advantageously formed as a valveblock by exploiting the so-called cartridge technique, this replacingseparate components.

After the automatic pressure valve selection the truck driver orcorresponding operator uses the operating valve 9 of the roll jaws 5' inthe normal manner, when the pressure valve selected on the basis of theidentifier 2 limits the pressure of the hydraulic oil going to thecylinder 8 through hydraulic line 15 to a certain maximum pressure. Atthis pressure the hydraulic oil flow produced by pump 7 begins to travelthrough the limiting pressure valve back to the return line 14.

The compressive force directed onto the paper roll 6 is determined inaccordance with the pressure of the hydraulic oil lead to the hydrauliccylinder 8 and here in particular to its piston rod 5b side end.

Naturally the connection at the compression side of the cylinder may bein another kind of roll jaws also on the piston side. There are numerousdifferent kinds of roll jaws with various types of mechanisms and inthese more than one hydraulic cylinders are often used.

In the second advantageous form of application in accordance with theinvention a single electrical pressure valve is used as the adjustmentmember 4, in which case the control unit 3 directs adjustment member 4,from which there is then a return connection 19 to the control unit 3 toadjust by means of the adjustment member 4 the pressure steplessly tocorrespond to the identifier information and thus the force directedonto the paper roll 6 being handled by the roll jaws. In place of thereturn connection the pressure valve may have two or more adjustmentvalues stepped in relation to one another set by electrical adjustmentcircuits, of which the control unit 3 selects one.

The drawings and the related description are only intended to illustratethe invention under discussion. In terms of details the method inaccordance with the invention and the system for setting the hydraulicpressure influencing the hydraulic grab member under discussion may bevaried within the terms of the accompanying Patent Claims.

We claim:
 1. A system for setting the hydraulic pressure influencing ahydraulic grab member (5), which system comprises a hydraulic operatingdevice including a hydraulic cylinder (8) for the grab member (5), asource of hydraulic pressure, and a pressure adjustment device,characterized in that a control unit (3) is connected to the adjustmentdevice (4), the control unit (3) being linked to a reading device (1),by means of which an identifier (2) on the piece (6) being handled canbe read, the identifier (2) either directly or indirectly expressing theforce that may be directed onto the piece (6) by the grab member (5);atleast two electric pressure valves (4a, 4b, . . . ) which are set todifferent pressure values; and a low-pressure hydraulic oil return line(14), characterized in that each pressure valve (4a, 4b, . . . ) isconnected between a hydraulic line (15) of the compression side of thehydraulic cylinder (8) and the aforementioned return line (14).
 2. Asystem in accordance with claim 1, wherein each pressure (4a, 4b, . . .) is connected to the control unit 93), so that at least one of thepressure valves (4a, 4b, . . . ) at a time can be selected to limit thehydraulic pressure going to the hydraulic cylinder (8) of the grabmember (5).
 3. A system for setting the hydraulic pressure influencing ahydraulic grab member (5), which system comprises a hydraulic operatingdevice including a hydraulic cylinder (8) for the grab member (5), asource of hydraulic pressure, and a pressure adjustment device,characterized in that a control unit (3) is connected to the adjustmentdevice (4), the control unit (3) being linked to a reading device (1),by means of which an identifier (2) on the piece (6) being handled canbe read, the identifier (2) either directly or indirectly expressing theforce that may be directed onto the piece (6) by the grab member (5);atleast two electric pressure halves (4a, 4b, . . . ) which are set todifferent pressure values; and each pressure valve (4a, 4b, . . . ) isconnected to the control unit (3), in which case at least one of thepressure valves (4a, 4b, . . . ) at a time can be selected to limit thehydraulic pressure going to the hydraulic cylinder (8) of the grabmember (5).
 4. A system for setting the hydraulic pressure influencing ahydraulic grab member (5), which system comprises a hydraulic operatingdevice including a hydraulic cylinder (8) for the grab member (5), asource of hydraulic pressure, and a pressure adjustment device,characterized in that a control unit (3) is connected to the adjustmentdevice (4), the control unit (3) being linked to a reading device (1),by means of which an identifier (2) on the piece (6) being handled canbe read, the identifier (2) either directly or indirectly expressing theforce that may be directed onto the piece (6) by the grab member (5);theadjustment device (4) comprises one electrical pressure regulationvalve; and a return connection (19) from the pressure regulation valveto the control unit (3), by means of which the hydraulic pressure goingto the hydraulic cylinder (8) operating the grab member (5) can beadjusted steplessly.
 5. A system for setting the hydraulic pressureinfluencing a hydraulic grab member (5), which system comprises ahydraulic operating device including a hydraulic cylinder (8) for thegrab member (5), a source of hydraulic pressure, and a pressureadjustment device, characterized in that a control unit (3) is connectedto the adjustment device (4), the control unit (3) being linked to areading device (1), by means of which an identifier (2) on the piece (6)being handled can be read, the identifier (2) either directly orindirectly expressing the force that may be directed onto the piece (6)by the grab member (5);the adjustment device (4) comprises oneelectrical pressure regulation valve; and at least two different openingpressure values are set for the pressure valve by means of electricalcontrol circuits, of which values the control unit (3) selects one.